We have yet to make a decision on this. We asked our Kickstarter backers through a survey if they'd be okay with us releasing him to the public eventually, but unfortunately the responses were very mixed.

How does one recruit Citlalli?I found her while exploring and before entering Tenochtitlan. After a one night stand I can only trade with those Amazons. There are no recruit options for me as it seems... Is it because my character already married Tayanna?

You have to accept the quest from Momoztli, the high priest in Tenochtitlan. There are a fair few ways to go through that quest, and it should be obvious which ones will lead to Citlalli joining you, and which ones will not.